(a) Field of the Invention
The present invention relates to a skew correction mechanism and, more particularly, to a technique for correcting a skew movement of a roll paper in a printer etc. The present invention also relates to a printer having such a skew correction mechanism.
(b) Description of the Related Art
A printer having a conventional skew correction mechanism for correcting a skew feed of a roll paper, or continuous paper, is described in Patent Publication No. JP-A-2(1990)-75553, for example. The printer described therein has a driving roller and a driven roller supported to oppose each other for skew correction. The skew amount of the roll paper is calculated based on a skew signal from a skew sensor mounted on the printer body to control the distance between the rotational shafts of both the rollers. As a result, the clamping force by which the roll paper is held between the rollers is changed along the transverse direction of the roll paper, thereby correcting the skew of the roll paper.
In the skew correction mechanism as described above, the change of the distance between the rotational shafts of both the rollers sometimes involves jamming of the roll paper by an excess clamping force for the roll paper, and also prevents accurate feed rate of the roll paper.
Some small-sized printers using a roll paper have a guide along the path route of the roll paper. The guide generally comprises a guide shaft extending in the transverse direction for guiding the roll paper thereon while changing the direction of the feed of the roll paper to stabilize the feed. In this type of the small-sized printer, the skew amount of the roll paper is generally large because the rolling force of the roll paper during fabrication thereof is not always constant along the transverse direction of the roll paper, because the radius and alignment of the guide shaft is not always constant along the axis thereof, and because a small amount of misalignment is generally involved when the roll paper is loaded on the printer. Accordingly, if the small-sized printer is provided with the skew correction mechanism proposed in the Patent Publication as mentioned above, the skew correction mechanism is not always effective to correct the skew feed of the roll paper.